OSTEICHTHYES

Characters & Anatomy

The Class Osteichthyes consists
of the bony fishes and is the largest class of vertebrates, with
over 24,000 species. These fishes have a
skeleton much stiffer than that of the cartilaginous fish (sharks). Bony
fish have an excellent sense of smell, like sharks and rays, but their sense
of vision is also excellent.

Bony fishes
range in size from the very small Philippine Goby Mugilogobius parvus (top
left), which is only about
10 mm long, to the ocean sunfish Mola mola, which can grow
up to 4 m in length and 1500kg in weight (top right).

As well as many vertebrae
for structural support and calcium storage, the bony fishes have
special adaptations to control their buoyancy. A special organ
called the swim
bladder acts as a
gas-filled chamber to control their depth in the water.

Another prominent feature
of the bony fishes is the operculum. This constitutes the lateral
fleshy grooves on the fish that cover the chambers housing the
gills. The operculum allows the fish to
breathe (even if it is not swimming) by moving water currents
over the gills. Other features include paired
fins, dermal scales in the skin (in most species) and numerous
vertebrae.